The present invention relates to a universal switched power converter that is capable of receiving a broad range of voltage levels, of both high direct current (DC) voltage coming from a source of rectified alternating current (AC) voltage and low direct current (DC) voltage coming from a battery that supplies backup power, and transforms the voltage received to another voltage level regulated and adequate for being supplied to at least one load.
Thus, the universal switched power converter is highly versatile, has a high overall efficiency and both its operation and its control are straightforward.
A switched power converter for being connected indistinctly to an alternating current (AC) power line or to a direct current (DC) voltage source, and converting the received voltage to a voltage adequate for a load, is known from the U.S. Pat. No. 5,414,610, being included in the present application by reference.
According to the power converter proposed in this document, it comprises a first pair of input terminals for receiving a voltage from an AC mains and a second pair of input terminals for receiving a voltage from a DC voltage source, converting the received voltage into a voltage level adequate for a load.
Each one of the foregoing pairs of input terminals are respectively connected to a primary circuit including a switching device; control means drive the switching of the two switching devices in order to store energy in at least one primary winding of a transformer during the conducting period of both switching devices, which are switched simultaneously, that is, their conducting and non-conducting periods coincide; and said energy is released into a secondary winding of the transformer in order to supply the voltage level to the load, during the non-conducting period of said switching devices.
The power converter proposed by the U.S. Pat. No. 5,414,610 makes an inefficient use of the transformer due to the operating mode of the switching devices.
Therefore, the overall efficiency of the power converter is low, and signifies a drawback for applications in which there is a requirement for devices of reduced size and high performance.
Consequently, there is a need to develop a switched power converter comprising a reduced number of switching elements and having high overall efficiency.
The universal switched power converter of the present invention carries out the conversion of a broad range of input voltages, from a voltage source, to an output voltage desired for one or more loads. Said conversion is performed with a high overall efficiency since it has a forward topology.
The universal switched power converter has a transformer that comprises a first winding divided into two parts having, consequently, an intermediate tap, and a second winding, which is connected in cascade with rectifying means and with filter means.
According to the voltage level received from the power source, the voltage is applied through a part of the first winding or through the complete first winding. Thus, when the input voltage is close to a first predetermined voltage value and a second switching element is in a conducting state, a first current flows through the part of the first winding comprised between the end of the first winding connected to a first input terminal and the intermediate tap and through the second switching element connected to the intermediate tap and to a second input terminal.
When the input voltage applied across the input terminals is close to a second predetermined voltage value and the first switching element is in a conducting state, a third current flows through the two parts of the first winding comprised between the end of the primary winding connected to the first input terminal and the end of the first winding connected to a first switchable element connected, in turn, in series with a first switching element connected to the second input terminal.
It is to be pointed out that the second predetermined voltage value is greater that the first predetermined voltage value. In brief, depending on the voltage level received from the power source, the voltage is applied to a common part of the first winding or to the complete first winding.